# CVE-2025-37913: net_sched: qfq: Fix double list add in class with netem as child qdisc

> A double list addition in the Linux kernel QFQ scheduler with netem child qdiscs causes memory corruption, potentially leading to system crashes or code execution.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 20 May 2025
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2025-37913, DEBIAN-CVE-2025-37913, GHSA-5363-pqw5-qgr2, ROOT-OS-DEBIAN-11-CVE-2025-37913, ROOT-OS-DEBIAN-12-CVE-2025-37913, ROOT-OS-UBUNTU-2204-CVE-2025-37913, ROOT-OS-UBUNTU-2404-CVE-2025-37913, UBUNTU-CVE-2025-37913

## What is CVE-2025-37913?

CVE-2025-37913 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 20 May 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

net_sched: qfq: Fix double list add in class with netem as child qdisc

As described in Gerrard's report [1], there are use cases where a netem
child qdisc will make the parent qdisc's enqueue callback reentrant.
In the case of qfq, there won't be a UAF, but the code will add the same
classifier to the list twice, which will cause memory corruption.

This patch checks whether the class was already added to the agg->active
list (cl_is_active) before doing the addition to cater for the reentrant
case.

[1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/

Weakness: CWE-415 (Double Free)

## Which versions are affected by CVE-2025-37913?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2025-37913?

Apply the vendor's patch.

## Is CVE-2025-37913 being exploited?

There is no known exploitation of CVE-2025-37913 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-37913 and fix it if it is affected.

What it is: CVE-2025-37913 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 20 May 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-37913 in the wild and no public exploit code.

Affected product: Debian Debian Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-37913/ (Markdown: https://insights.sbomify.com/CVE-2025-37913/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-37913
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-37913
- OSV: https://osv.dev/vulnerability/CVE-2025-37913

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-37913/
Summaries are generated and may contain mistakes; the official description above is the record.